Comment by blake1
5 years ago
As mentioned in the article, solar power is insanely cheap. So while you are right that a kWh of solar is not, on average, as valuable as a kWh of semidispatchable coal, the insane cheapness means that at some point, it is economical to massively overbuild renewable and decommission fossil fuel plants. You provide no evidence for the implausible claim that solar causes emissions to go up: your argument is only that the emissions reducing effect is muted, which may be true.
Also, while storage would be helpful, it is not the only way to enable a renewable transition. Additional transmission is enormously helpful: as the sun goes down on California, the wind is picking up in the Midwest. And don’t forget demand response: if smart thermostats received price signals (maybe we should precool this house...) that would alleviate the evening ramp-up issue.
So I claim we’ll need less storage than “a whole day’s usage”. But the learning curve applies to batteries as well! This storage won’t cost as much anyway.
The whole issue of intermittency is overrated. While a single solar panel might generate intermittently, the solar fleet across a whole state generates more predictably.
I am predicting that grid emissions will come down a lot over the coming decades. Partially I’m predicting the past: they’ve already come down, a lot!
Exactly, the only thing limiting solar at this point is the rate of investment. Wind and hydro etc have a huge role, but for some back of the envelope estimates.
On the storage issue, at ~100$/kWh batteries that do a conservative 1,000 cycles are ~10c/kWh stored + generation costs + conversion inefficiency. Take current unsubsidized grid solar prices of 2c/kWh solar and double that for 4c/kWh as a conservative redundant safety margin. Tracking solar for example has much better morning and evening generation though at slightly higher prices.
If 2/3 of your electricity is at 4c/kWh and 1/3 is at 15c/kWh that’s 7.7c/kWh for pure solar 24/7 including peaking power needs. Obviously a specific mix of generation determines storage needs, but those are also really pessimistic estimates.
PS: Hydro power is 6.1% of the total U.S. electricity generation. If 80% of that is released at night that’s a huge reduction in storage needed. Similarly transmitting power east or west makes a large difference in storage needs.
Hydro isn't quite so fungible, I think a couple areas account for most the hydro generation.
It doesn't matter that if solar/wind is cheap (or even zero) because you still have to have an alternate power source for when your intermittent power has gone AWOL. You need cheap grid-scale storage, which doesn't exist at the moment.
Or some other dispatchable low-carbon energy source, which also doesn't really exist at the moment. Load-following nuclear reactors (hooked to thermal storage) could do this physically but a lot has to happen to get the cost down. Meanwhile, various CCS options could play a role if there's a solution for safely storing vast quantities of carbon out of the atmosphere.
I don't know about its efficacy, but my favorite means of mass energy storage is a gravity battery: literally stacking heavy blocks in a huge tower, which are raised and lowered based on energy demands by automated cranes.
https://en.wikipedia.org/wiki/Energy_Vault
At best a 'gravity battery' is as efficient as hydroelectric, since pumped-storage is a gravity battery. Towers, trains, spinning flywheels are high-maintenance by comparison. The technology for pumped-storage requires a supply of water and a high place to pump it to. Used around the world (Europe & US, at least) since 1890s.
Bath County, VA: capacity 24GWh, since 1985
https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit...
Dinorwig Power Station, Wales: capacity 9.1GWh
https://www.theregister.co.uk/2016/05/16/geeks_guide_electri...
Worldwide, today
https://en.wikipedia.org/wiki/List_of_pumped-storage_hydroel...
Hmm I'm not so sure about that: gravity is weak.
In some news article they say Energy Vault uses 35-ton blocks hoisted up to ~150 m - while it sounds impressive, that's only 14.3kWh (assuming 100% conversion efficiency), or about 1/7 of a single Tesla Model S (100kWh).
When I briefly looked into this, my takeaway was that the energy density (and thus price) is much, much lower than needed to compete with other storage mechanisms.
As another poster said, gravity is relatively weak compared to the other forces.
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There are many nifty schemes like this, such as compressed air, cryogenics, hydrogen, thermal, different battery chemistries, etc. Efficacy in the form economic scalability is the crucial characteristic.
Seems like a novel take on the same principal behind pumped storage hydro systems. But, at a max of 80MWh of storage, you'd need hundreds of them to match a single pumped hydro facility, which often have 10,000+ MWh of storage.
Storage would be some combination of diurnal storage (batteries, say) and long term storage (hydrogen). The former benefits from high efficiency; the latter from lower capital cost. There is also thermal storage (an order of magnitude cheaper than batteries) for any application involving heating or cooling, including industrial users of heat.
Hydrogen... which can then be put back through a fuel cell to produce electrickery. The germans are looking at this. I believe.
> if smart thermostats received price signals (maybe we should precool this house...) that would alleviate the evening ramp-up issue.
Is there an existing model for retail intraday rates? Would intraday rates be desirable for all market participants?
"Add area for curtailment data?" https://github.com/tmrowco/electricitymap-contrib/issues/236...